Glass panel unit

ABSTRACT

The glass panel unit includes a first glass panel, a second glass panel, a seal, an evacuated space, and at least one spacer. The second glass panel is placed opposite the first glass panel. The seal with a frame shape hermetically bonds the first glass panel and the second glass panel to each other. The evacuated space is enclosed by the first glass panel, the second glass panel, and the seal. The at least one spacer is placed between the first glass panel and the second glass panel. The at least one spacer has a height H 1  smaller than a height H 2  of the seal between the first glass panel and the second glass panel.

TECHNICAL FIELD

The present disclosure relates to glass panel units.

BACKGROUND ART

There has been known a glass panel unit in which two or more glass panels are stacked with one or more gaps in-between to form one or more hermetically enclosed spaces, and the spaces are made to be in a vacuum state. This type of glass panel unit is referred to as a multiple glass panel. This glass panel unit has high thermal insulating properties. It is important that the glass panel unit keeps the vacuum state.

There has been proposed use of spacers to keep a thickness of the evacuated space inside the glass panel unit. The spacers are materials sandwiched between the two glass panels. Placement of spacers is requested to produce fine glass panel units. JP 2003-306354 A discloses adjusting arrangement of spacers (gap keeping members) to suppress internal stress from exceeding predetermined value. In this technique, to suppress the internal stress, a distance between the outermost row of spacers and the end of the glass plate is shortened. However, this technique aims to suppress the internal stress which may occur in formation of the evacuated space, but seems to be insufficient to resistance to external impact.

SUMMARY OF INVENTION

An object of the present disclosure would be to propose a glass panel unit with increased strength.

The glass panel unit is disclosed. The glass panel unit includes: a first glass panel, a second glass panel, a seal, an evacuated space, and at least one spacer. The second glass panel is placed opposite the first glass panel. The seal with a frame shape hermetically bonds the first glass panel and the second glass panel to each other. The evacuated space is enclosed by the first glass panel, the second glass panel, and the seal. The at least one spacer is placed between the first glass panel and the second glass panel. The at least one spacer has a height smaller than a height of the seal between the first glass panel and the second glass panel.

The glass panel unit of the present disclosure can have excellent strength.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic section of a glass panel unit of one example.

FIG. 2 is a schematic plan of the glass panel unit of the example.

FIG. 3A and FIG. 3B are schematic diagrams for illustration of functions of glass panel units. FIG. 3A relates to a case where spacers have their heights smaller than a height of the seal, and FIG. 3B relates to a case where the spacers have their heights larger than the height of the seal.

FIG. 4 is a perspective view of the glass panel unit at a step of a method for manufacturing the same thereof.

FIG. 5 is a perspective view of the glass panel unit at another step of the method for manufacturing the same.

FIG. 6 is a perspective view of the glass panel unit at another step of the method for manufacturing the same.

FIG. 7 is a perspective view of the glass panel unit at another step of the method for manufacturing the same.

FIG. 8 is a schematic plan of a completed assembly of the glass panel unit.

FIG. 9 is a schematic section of the completed assembly of the glass panel unit.

FIG. 10 is a perspective view of the glass panel unit at another step of the method for manufacturing the same.

FIG. 11 is a schematic section of a glass panel unit of another example.

FIG. 12 is a schematic section of a glass panel unit of another example.

FIG. 13 is a graph showing results of test by a free falling ball method for glass panel units.

DESCRIPTION OF EMBODIMENTS

The following disclosure relates to glass panel units. In particular, the following disclosure relates to a glass panel unit where an evacuated space is formed between a pair of glass panels.

FIG. 1 and FIG. 2 show a glass panel unit 10 of one embodiment. The glass panel unit 10 of the present embodiment is a vacuum insulated glass unit. The vacuum insulated glass unit is a type of multiple glass panels including at least one pair of glass panels, and includes an evacuated space 50 between the pair of glass panels. Note that, in FIG. 2, to facilitate understanding of the internal structure only, the first glass panel 20 is illustrated with part (left and lower part) thereof being cutaway. Note that, upward, downward, left, and right directions in the figures are determined based on a direction of allowing reading reference numbers correctly.

The glass panel unit 10 includes the first glass panel 20, a second glass panel 30, a seal 40, the evacuated space 50, and spacers 70. The second glass panel 30 is placed opposite the first glass panel 20. The seal 40 with a frame shape hermetically bonds the first glass panel 20 and the second glass panel 30 to each other. The evacuated space 50 is enclosed by the first glass panel 20, the second glass panel 30, and the seal 40. The spacers 70 are placed between the first glass panel 20 and the second glass panel 30. The spacers 70 have heights smaller than a height of the seal 40 between the first glass panel 20 and the second glass panel 30.

In the glass panel unit 10, the height of the spacer 70 is smaller than the height of the seal 40. Accordingly, a structure with improved resistance to external impact can be formed. Therefore, the glass panel unit 10 excellent in strength can be produced.

The first glass panel 20 includes a body 21 determining a plan shape of the first glass panel 20, and a coating 22. The body 21 is rectangular and includes a first face (external face; upper face in FIG. 1) and a second face (internal face; lower face in FIG. 1) in a thickness direction which are parallel to each other. Each of the first face and the second face of the body 21 is a flat face. Examples of material of the body 21 of the first glass panel 20 may include soda lime glass, high strain point glass, chemically strengthened glass, non-alkaline glass, quartz glass, neoceram, and physically strengthened glass. Note that, the first glass panel 20 does not need to include the coating 22. The first glass panel 20 may be constituted by the body 21 only.

The coating 22 is formed on the second face of the body 21. The coating 22 may preferably be an infrared reflective film. Note that, the coating 22 is not limited to such an infrared reflective film but may be a film with desired physical properties.

The second glass panel 30 includes a body 31 determining a plan shape of the second glass panel 30. The body 31 is rectangular and includes a first face (internal face; upper face in FIG. 1) and a second face (external face; lower face in FIG. 1) in a thickness direction which are parallel to each other. Each of the first face and the second face of the body 31 is a flat face. Examples of material of the body 31 of the second glass panel 30 may include soda lime glass, high strain point glass, chemically strengthened glass, non-alkaline glass, quartz glass, neoceram, and physically strengthened glass. The material of the body 31 may be same as the material of the body 21. The body 31 has the same plan shape with the body 21. Stated differently, the second glass panel 30 has the same plan shape with the first glass panel 20.

The second glass panel 30 includes the body 31 only. In other words, the body 31 forms the second glass panel 30 by itself. The second glass panel 30 may include a coating. The coating may be formed on the first face of the body 31. This coating may have properties same as the coating 22 of the first glass panel 20.

The first glass panel 20 and the second glass panel 30 are arranged so that the second face of the body 21 and the first face of the body 31 face and parallel to each other. In other words, the first face of the body 21 is directed outward from the glass panel unit 10, and the second face of the body 21 is directed inward of the glass panel unit 10. Further, the first face of the body 31 is directed inward of the glass panel unit 10, and the second face of the body 31 is directed outward from the glass panel unit 10.Note that, as described later, the first glass panel 20 and the second glass panel 30 do not have perfectly flat surfaces, but may have curved surfaces which are slightly curved.

A thickness of the first glass panel 20 is not limited particularly, but may be in a range of 1 to 10 mm. A thickness of the second glass panel 30 is not limited particularly, but may be in a range of 1 to 10 mm. The first glass panel 20 and the second glass panel 30 may have the same thickness or different thicknesses. When the first glass panel 20 and the second glass panel 30 have the same thickness, formation of the glass panel unit 10 is facilitated.

In a plan view, outlines of the first glass panel 20 and the second glass panel 30 are aligned with each other. Therefore, the glass panel unit 10 can have good appearance. Further, handling of the glass panel unit 10 becomes easy. Further, a range of applications of the glass panel unit 10 can be expanded. Additionally, strength of the glass panel unit 10 is increased. Note that, the outlines of the first glass panel 20 and the second glass panel 30 may not be aligned with each other in a plan view. The plan view means a view of the glass panel unit 10 in the thickness direction thereof. The thickness direction of the glass panel unit 10 is identical to the height direction of the spacer 70.

In FIG. 1 and FIG. 2, the glass panel unit 10 further includes a gas adsorbent 60. The gas adsorbent 60 is placed inside the evacuated space 50. In the present embodiment, the gas adsorbent 60 has an elongated shape. The gas adsorbent 60 is formed on a second end (left end in FIG. 2) in the lengthwise direction of the second glass panel 30 to extend along the width direction of the second glass panel 30. In summary, the gas adsorbent 60 is placed on one end of the evacuated space 50. According to this arrangement, the gas adsorbent 60 can be unlikely to be perceived. In a case of directly placing the gas adsorbent 60 on a glass panel, placement of the gas adsorbent 60 can be facilitated. Note that, the gas adsorbent 60 may be provided in any position in the evacuated space 50.

The gas adsorbent 60 is used to adsorb unnecessary gas (for example, residual gas). The unnecessary gas may include gas emitted in forming the seal 40. The unnecessary gas may further include gas intruding into an inside through a gap in the seal 40. An increase in such gas may cause a decrease in the degree of vacuum and thus a decrease in the thermal insulating properties.

The gas adsorbent 60 includes a getter. The getter is a substance having properties of adsorbing molecules smaller than a predetermined size. The getter may be an evaporative getter. Examples of the evaporative getter may include zeolite and ion-exchanged zeolite.

The seal 40 encloses the evacuated space 50 completely and bonds the first glass panel 20 and the second glass panel 30 to each other hermetically. The seal 40 is placed between the first glass panel 20 and the second glass panel 30. The seal 40 has a rectangular frame shape. The evacuated space 50 has a degree of vacuum equal to or lower than a predetermined value. The predetermined value may be 0.1 Pa, for example. The evacuated space 50 may be formed by evacuation. The evacuation may include forming a hole for evacuation in at least one of the first glass panel 20, the second glass panel 30, and the seal 40 and removing gas from an inside. However, it is preferable that both the first glass panel 20 and the second glass panel 30 do not include any outlet by the following evacuation. In this case, it is possible to produce the glass panel unit 10 with an improved appearance. In FIG. 1, neither the first glass panel 20 nor the second glass panel 30 includes an outlet.

The evacuated space 50 can be made to be in a vacuum state by conducting evacuation while heating. Heating may lead to an increase in the degree of vacuum. Additionally, such heating may cause formation of the seal 40. A temperature for heating to form a vacuum state may be equal to or higher than 300° C. This condition may contribute to an increase in the degree of vacuum. A concrete method of forming the evacuated space 50 may be described later.

The seal 40 is formed of thermal adhesive. Examples of the thermal adhesive may include glass frit. Examples of the glass frit may include low-melting-point glass frit. Examples of the low-melting-point glass frit may include bismuth-based glass frit, lead-based glass frit, and vanadium-based glass frit. The seal 40 may be made of multiple thermal adhesives, as described below.

The seal 40 has a predetermined height. In FIG. 1, the height of the seal 40 is designated by reference sign H2. The height H2 of the seal 40 determines a distance T2 between the first glass panel 20 and the second glass panel 30 at a periphery of the glass panel unit 10. The height H2 of the seal 40 may be in a range of 10 to 1000 μm.

The seal 40 may protrudes outside from a gap between the first glass panel 20 and the second glass panel 30. The seal 40 may protrude to present beside one or both of a side surface of the first glass panel 20 and a side surface of the second glass panel 30. In some cases, a dimension of protruded part of the seal 40 in the thickness direction of the glass panel unit 10 may be larger than the distance between the first glass panel 20 and the second glass panel 30. Therefore, the height H2 of the seal 40 may be defined as a height (distance) between the first glass panel and the second glass panel.

Note that, an outline of the seal 40 may be aligned with the outlines of the first glass panel 20 and the second glass panel 30. Additionally, an end surface of the seal 40 may be flush with end surfaces of the first glass panel 20 and the second glass panel 30. When there is no uneven structure at boundaries between the seal 40 and the glass panels, appearance can be improved. The side surfaces of the glass panel unit 10 may be flat surfaces without uneven structures. The flat side surfaces can be formed by cutting glass substrates (materials of glass panels) described below along the seal 40. The flat side surfaces may be formed by cutting the completed assembly 110 by dividing the seal 40 (by shifting the position of the cutting line 900 in FIG. 8 described below). Alternatively, the flat side surfaces can be formed by polishing sides of the glass panel unit 10 after cutting of the glass substrates. In this regard, the seal 40 may be polished, the glass panel may be polished, or both may be polished. Note that, the flat side surfaces can be formed by cutting the glass panels along the outline of the seal 40.

The seal 40 may preferably include materials for keeping the distance between the first glass panel 20 and the second glass panel 30. Hence, the space between the first glass panel 20 and the second glass panel 30 can be formed securely. Examples of the materials for keeping the distance between the first glass panel 20 and the second glass panel 30 may include particles and wires. The particles can be easily blended to thermal adhesive, and thus can keep the distance between the first glass panel 20 and the second glass panel 30.

The seal 40 may include particles for keeping the distance between the first glass panel 20 and the second glass panel 30. The particles each may have properties of retaining its original shape even if receiving heat for forming the seal 40 from thermal adhesive. The particles are sandwiched between the two glass panels. Therefore, even when the two glass panels are bonded, the gap between the two glass panels is not smaller than a particle size. Thus, the seal 40 is not crushed but can ensure the height. Examples of the particles may include metal particles and high-melting-point glass particles. Examples of the particles may further include beads. The height H2 of the seal 40 can be adjusted by selecting sizes of the particles.

The glass panel unit 10 includes multiple spacers 70. The multiple spacers 70 are used to keep a predetermined interval between the first glass panel 20 and the second glass panel 30. The multiple spacers 70 allow reliably ensuring the space between the first glass panel 20 and the second glass panel 30. The number of spacers 70 may be one but preferably two or more in order to keep a thickness of a space between the glass panels. Provision of multiple spacers 70 may lead to an increase in strength of the glass panel unit 10.

The multiple spacers 70 are placed inside the evacuated space 50. In more detail, the multiple spacers 70 are placed at individual intersections of an imaginary rectangular lattice.

For example, an interval between the multiple spacers 70 may be in a range of 1 to 10 cm, and in one example may be 2 cm. Note that, sizes of the spacers 70, the number of spacers 70, intervals between the spacers 70, and pattern of arrangement of the spacers 70 may be appropriately determined.

Each spacer 70 is made of light-transmissive material. Thus, the multiple spacers 70 are unlikely to be perceived. Note that, each spacer 70 may be made of opaque material, providing that it is sufficiently small. Material of the spacers 70 is selected so that crush of the spacers 70 does not occur during a first melting step, an evacuating step, and a second melting step which are described later. For example, the material of the spacers 70 is selected to have a softening point (softening temperature) higher than a first softening point of a first thermal adhesive and a second softening point of a second thermal adhesive.

The spacer 70 may be made of polymer. Thereby the spacer 70 has elasticity inherently. Thus, resistance to impact of the glass panel unit 10 can be improved. The spacer 70 may be made of one or more films of polymer. The spacer 70 may be made of a stack of two or more films of polymer, or may be made of a single film of polymer. In the case where the spacer 70 is made of a stack of two or more films of polymer, the films of polymer may be bonded to each other with bond. The stack may be formed in advance before the two glass panels are bonded to each other. The stack can facilitate adjustment of the height of the spacer 70. The stack is trimmed to have an appropriate size and thus is used as the spacer 70. A preferable example of the polymer may be polyimide. The polyimide is high in strength and resistance to heat. The polyimide with benzoxazole structures is more preferably used.

Each spacer 70 has a solid cylindrical shape. Each spacer 70 has a predetermined height. In FIG. 1, the height of the spacer 70 is designated by reference sign H1. For example, each spacer 70 may have a diameter ranging from 0.1 to 10 mm and the height H1 ranging from 10 to 1000 μm. Note that, each spacer 70 may have a desired shape such as a solid prismatic shape and a spherical shape. The heights H1 of the multiple spacers 70 determine the distance T1 between the first glass panel 20 and the second glass panel 30 at a center of the glass panel unit 10. The distance T1 determines the thickness of the evacuated space 50. The distance T1 is equal to the thickness of the evacuated space 50. The evacuated space 50 may have a thickness ranging from 10 to 1000 μm, for example.

In the present embodiment, as for the height H1 of the spacer 70 and the height H2 of the seal 40, a relation of H1<H2 is satisfied. Note that, a difference between the height H1 of the spacer 70 and the height H2 of the seal 40 is too small to perceive with naked eyes. Such a difference is unlikely to be perceivable also due to the fact that the height H1 of the spacer 70 and the height H2 of the seal 40 per se are small (both may be equal to or smaller than 1000 μm). When watching the glass panel unit 10 by naked eyes, H1 and H2 appear to be almost equal to each other. However, the height relation of H1<H2 can be confirmed by precise measurement. FIG. 1 shows that a gap between the first glass panel 20 and the second glass panel 30 becomes greater at ends of the glass panel unit 10. Precise observation of the glass panel unit 10 may show that one or both of the first glass panel 20 and the second glass panel 30 are depressed at center part thereof. Stated differently, one or both of the first glass panel 20 and the second glass panel 30 may sag inward at center part thereof. Stated differently, one or both of the first glass panel 20 and the second glass panel 30 may be rolled back. Stated differently, one or both of the first glass panel 20 and the second glass panel 30 may be curved. Stated differently, one or both of the first glass panel 20 and the second glass panel 30 may be warped inward. Note that, the height H1 of the spacer 70 and the height H2 of the seal 40 mean the height of the spacer 70 and the height of the seal 40 after formation of the glass panel unit 10. The heights H1 and H2 do not mean heights before formation of the glass panel unit 10 or heights during formation of the glass panel unit 10. This is because that the height of the spacer 70 and the height of the seal 40 may change in formation of the glass panel unit 10.

The difference between the height H1 of the spacer 70 and the height H2 of the seal 40 is not limited particularly but may preferably be larger than 1 μm, more preferably 5 μm, and most preferably 10 μm. The height H1 of the spacer 70 may be equal to or smaller than 95% of the height H2 of the seal 40, and may be equal to or smaller than 90% of the height H2 of the seal 40. Note that, an excessively large difference between the height H1 of the spacer 70 and the height H2 of the seal 40 may prevent formation of the stable evacuated space 50, and thus the difference may be set appropriately so that the evacuated space 50 is formed stably. The difference between the height H1 of the spacer 70 and the height H2 of the seal 40 are not limited particularly, but may be preferably smaller than 200 μm, more preferably 100 μm, and most preferably 50 μm. Further, the height H1 of the spacer 70 may be equal to or larger than 70% of the height H2 of the seal 40, and may be equal to or larger than 80% of the height H2 of the seal 40.

In the glass panel unit 10, the distance between the first glass panel 20 and the second glass panel 30 may vary in different locations. The distance between the first glass panel 20 and the second glass panel 30 at ends of the glass panel unit 10, that is an outside of the seal 40, is T2. The distance between the first glass panel 20 and the second glass panel 30 at the center part of the glass panel unit 10, that is center part of the evacuated space 50, is T1. In this regard, the distance T1 and the distance T2 may satisfy a relation of T1<T2. As for the evacuated space 50, the distance between the first glass panel 20 and the second glass panel 30 at center part may be smaller than the distance between the first glass panel 20 and the third glass panel 30 at a vicinity of the seal 40. As for the evacuated space 50, the distance between the first glass panel 20 and the second glass panel 30 may become smaller toward the center part. The distance between the first glass panel 20 and the second glass panel 30 inside the evacuated space 50 is defined as the thickness of the evacuated space 50.

Note that, the multiple spacers 70 may have the same height or may have different heights. When all the multiple spacers 70 have the same height, production of the glass panel unit 10 can be facilitated. When the evacuated space 50 has different thicknesses in different locations, the heights of the multiple spacers 70 may vary. The multiple spacers 70 may vary in production of the glass panel unit 10. This is because that each spacer 70 is sandwiched between the two glass panels. The multiple spacers 70 may have the same height before formation of the glass panel unit 10 but the multiple spacers 70 may have different heights after formation of the glass panel unit 10. In this case, production of the glass panel unit 10 can be facilitated. Alternatively, the multiple spacers 70 may have different heights even before formation of the glass panel unit 10.

FIG. 3A and FIG. 3B are schematic diagrams for illustration of functions of glass panel units. FIG. 3A relates to a case where spacers 70 have their heights H1 smaller than the height H2 of the seal 40. FIG. 3B relates to a case where the spacers 70 have their heights H1 larger than the height H2 of the seal 40. In summary, the case shown in FIG. 3A satisfies a relation of H1<H2, and the case shown in FIG. 3 B does not satisfy this relation. As for FIG. 3A and FIG. 3B, to facilitate understanding of the relation of the heights of the spacer 70 and the seal 40, these heights are magnified (emphasized). Further, in FIG. 3A and FIG. 3B, the glass panel units 10 are briefly illustrated.

As shown in FIG. 3A, when the relation of H1<H2 is satisfied, the two glass panels are bonded to each other while compressed. In this case, the two glass panels slightly change in shapes to come close to each other, and strength can be increased. Especially, strength in a direction perpendicular to the surfaces of the glass panel unit 10 can be improved. As indicated by arrows, forces are applied to the two glass panels so as to move them close to each other. In contrast, as shown in FIG. 3B, when the relation of H1<H2 is not satisfied, the two glass panels are bonded to each other while pulled. In this case, as indicated by arrows, forces are applied to the two glass panels so as to move them away from each other. In this case, the two glass panels slightly change in shapes in a direction in which they move away from each other, and strength is likely to be decreased.

It is inferred that an increase and a decrease in the strength of the glass panel units 10 illustrated in FIG. 3A and FIG. 3B are caused by stress on the glass panels. In FIG. 3A, stress applied on the glass panels in inward directions (see arrows). Therefore, the structure formed by the two glass panel can have increased strength. In contrast, in FIG. 3B, stress applied on the glass panels in outward directions (see arrows). Therefore, the structure formed by the two glass panel tends to have decreased strength. In conclusion, it is considered that difference in stress may influence strength of the glass panel unit 10.

Further, it is inferred that an increase and a decrease in the strength of the glass panel units 10 illustrated in FIG. 3A and FIG. 3B are caused by a process of formation of the seal 40. In more detail, in forming the seal 40 from the thermal adhesive, the thermal adhesive is compressed in the case of FIG. 3A but the thermal adhesive is not compressed in the case of FIG. 3B. The thermal adhesive influences on adhesion between glass panels. For this reason, it is considered that adhesion between the two glass panel may be weaker in the case of FIG. 3B than in the case of FIG. 3A. Thus, strength of the glass panel unit 10 shown in FIG. 3B may decrease. This is confirmed from a result of test by a free-falling ball method for the glass panel unit 10. The result reveals that glass is severely damaged at a periphery of the seal 40 in addition to part struck by a ball. Additionally, a lot of damages were observed in the glass panel facing the glass panel receiving impact. This phenomenon can be observed even when the glass panel unit 10 is formed to satisfy the height relation of H1=H2. When the height H2 of the seal 40 is larger than the heights of the spacers 70, this phenomenon can be suppressed.

Hereinafter, a method for manufacturing the glass panel unit 10 is described with reference to FIG. 4 to FIG. 10. FIG. 4 to FIG. 10 show an example of the method for manufacturing the glass panel unit 10. The glass panel unit 10 shown in FIG. 1, FIG. 2, and FIG. 3A can be produced by the method illustrated in FIG. 4 to FIG. 10. According to the method illustrated in FIG. 4 to FIG. 10, the glass panel unit 10 devoid of any outlet can be produced.

To produce the glass panel unit 10, first of all a temporary assembly 100 is prepared as shown in FIG. 4 to FIG. 6 and subsequently a completed assembly 110 shown in FIG. 7 to FIG. 9 is prepared by a predetermined process. Thereafter, as shown in FIG. 10, the glass panel unit 10 can be obtained by cutting a particular part from the completed assembly 110.

The method for manufacturing the glass panel unit 10 includes a preparation step, an assembling step, a hermetically enclosing step, and a removing step. Note that, the preparation step can be omitted.

The preparation step is a step of preparing a first glass substrate 200, a second glass substrate 300, a frame 410, a partition 420, the gas adsorbent 60, and the multiple spacers 70. According to the preparation step, an inside space 500, a gas passage 600, and an outlet 700 can be formed.

The first glass substrate 200 is a substrate to give the first glass panel 20. As shown in FIG. 9, the first glass substrate 200 includes a glass plate 210 determining a plan shape of the first glass substrate 200, and a coating 220. The glass plate 210 is a rectangular flat plate and includes a first face and a second face in a thickness direction which are parallel to each other. The coating 220 is formed on the second face of the glass plate 210. The glass plate 210 forms the body 21 of the first glass panel 20. The first face of the glass plate 210 corresponds to the first face of the body 21, and the second face of the glass plate 210 corresponds to the second face of the body 21. The coating 220 forms the coating 22 of the first glass panel 20. Note that, the coating 220 may be optional.

The second glass substrate 300 is a substrate to give the second glass panel 30. As shown in FIG. 9, the second glass substrate 300 includes a glass plate 310 determining a plan shape of the second glass substrate 300. The glass plate 310 is a rectangular flat plate and includes a first face and a second face in a thickness direction which are parallel to each other. The second glass substrate 300 serves as a base for the body 31 of the second glass panel 30. The first face of the glass plate 310 corresponds to the first face of the body 31, and the second face of the glass plate 310 corresponds to the second face of the body 31. The glass plate 310 has the same plan shape and plan size as the glass plate 210. In other words, the second glass substrate 300 has the same plan shape as the first glass substrate 200. Further, the glass plate 310 has the same thickness as the glass plate 210. The second glass substrate 300 includes the glass plate 310 only. In other words, the glass plate 310 forms the second glass substrate 300 by itself.

The second glass substrate 300 is placed opposite the first glass substrate 200. In more detail, the first glass substrate 200 and the second glass substrate 300 are arranged so that the second face of the glass plate 210 and the first face of the glass plate 310 face and parallel to each other.

The frame 410 is placed between the first glass substrate 200 and the second glass substrate 300 to hermetically bond the first glass substrate 200 and the second glass substrate 300 to each other. Thereby, as shown in FIG. 6, the inside space 500 enclosed by the frame 410, the first glass substrate 200, and the second glass substrate 300 is formed.

The frame 410 is formed of thermal adhesive (the first thermal adhesive with the first softening point). Examples of the first thermal adhesive may include glass frit. Examples of the glass frit may include low-melting-point glass frit. Examples of the low-melting-point glass frit may include bismuth-based glass frit, lead-based glass frit, and vanadium-based glass frit. The first thermal adhesive may preferably include particles for ensuring a gap between the two glass panels. The particles can determine the height of the frame 410. The particles can determine the seal 40.

The frame 410 has a rectangular frame shape. The frame 410 has the same plan shape as each of the glass plates 210 and 310, but the frame 410 has a smaller plan size than each of the glass plates 210 and 310. As shown in FIG. 4, the frame 410 is formed to extend along an outer periphery of the second glass substrate 300. In other words, the frame 410 is formed to cover an almost entire region on the second glass substrate 300.

The partition 420 is placed inside the inside space 500. As shown in FIG. 6, the partition 420 divides the inside space 500 into an evacuation space 510 and a gas passage space 520. The evacuation space 510 is a space to be evacuated later, and the gas passage space 520 is a space used for evacuating the evacuation space 510. The partition 420 is formed between a first end (right end in FIG. 4) and a center of the second glass substrate 300 in a lengthwise direction (left and right direction in FIG. 4) of the second glass substrate 300 so that the evacuation space 510 is larger than the gas passage space 520.

The partition 420 includes a wall part 421 and a pair of closing parts 422 (a first closing part 4221 and a second closing part 4222). The wall part 421 is formed to extend along a width direction of the second glass substrate 300. In FIG. 6, the width direction means a direction extending along a short side of the temporary assembly 100 with a rectangular shape. Note that, the wall part 421 has opposite ends in a lengthwise direction not in contact with the frame 410. The pair of closing parts 422 extends from the opposite ends in the lengthwise direction of the wall part 421 toward the first end in the lengthwise direction of the second glass substrate 300.

The partition 420 is formed of thermal adhesive (the second thermal adhesive with the second softening point). Examples of the second thermal adhesive may include glass frit. Examples of the glass frit may include low-melting-point glass frit. Examples of the low-melting-point glass frit may include bismuth-based glass frit, lead-based glass frit, and vanadium-based glass frit. The second thermal adhesive is same as the first thermal adhesive, and the second softening point is equal to the first softening point. The second thermal adhesive may preferably include particles for ensuring a gap between the two glass panels. The particles can determine the height of the partition 420. The particles can determine the seal 40.

The gas adsorbent 60 is placed inside the evacuation space 510. In more detail, the gas adsorbent 60 is placed on one end of the evacuation space 510. Further, the gas adsorbent 60 is positioned away from the partition 420 and the gas passage 600. Hence, it is possible to lower a probability that the gas adsorbent 60 prevents evacuation of the evacuation space 510.

The multiple spacers 70 are already described with reference to FIG. 1 and FIG. 2. Each spacer 70 may be formed of the stack of films. The spacer 70 can be produced by bonding two or more films of polymer with bond and then cutting them, for example. The preparation step may further include a step of preparing spacers 70. As shown in FIG. 4, the multiple spacers 70 may be arranged at predetermined intervals in longitudinal and lateral directions.

Note that, the height of the spacer 70 which is present as a separate part before included in the glass panel unit 10 may be different from the height of the spacer 70 after the glass panel unit 10 has been formed. The spacers 70 may be compressed in the height direction due to being sandwiched by the two glass panels. For this reason, the height of the spacer 70 before formation of the glass panel unit 10 may be equal to or larger than the height of the frame 410, for example. However, it is more preferable that the height of the spacer 70 before formation of the glass panel unit 10 be smaller than the height of the frame 410. Accordingly, the spacer 70 is unlikely to be crushed. Even if crush of the spacer 70 occurs, such crush is unlikely to be perceivable. Additionally, strength of the glass panel unit 10 can be more improved. The height of the partition 420 can be considered in the same manner as the height of the frame 410. It is preferable that the height of the spacer 70 before formation of the glass panel unit 10 be smaller than the height of the partition 420.

The gas passage 600 interconnects the evacuation space 510 and the gas passage space 520 in the inside space 500. The gas passage 600 includes a first gas passage 610 and a second gas passage 620. The first gas passage 610 is a space formed between the first closing part 4221 and part of the frame 410 facing the first closing part 4221. The second gas passage 620 is a space formed between the second closing part 4222 and part of the frame 410 facing the second closing part 4222. As a result of placing the partition 420 as described above, the gas passage 600 is formed.

The outlet 700 is a hole interconnecting the gas passage space 520 and an outside space. The outlet 700 is used for evacuating the evacuation space 510 by way of the gas passage space 520 and the gas passage 600. Therefore, the gas passage 600, the gas passage space 520, and the outlet 700 constitute an evacuation passage for evacuating the evacuation space 510. The outlet 700 is formed in the second glass substrate 300 to interconnect the gas passage space 520 and the outside space. In more detail, the outlet 700 is positioned in a corner of the second glass substrate 300.

The preparation step is performed for the aforementioned members. The preparation step includes first to sixth steps. Note that, the order of the second to sixth steps may be modified.

The first step is a step (substrate formation step) of forming the first glass substrate 200 and the second glass substrate 300. For example, in the first step, the first glass substrate 200 and the second glass substrate 300 are produced. The first step may include cleaning the first glass substrate 200 and the second glass substrate 300 if necessary.

The second step is a step of forming the outlet 700. In the second step, the outlet 700 is formed in the second glass substrate 300. Further, in the second step, the second glass substrate 300 is cleaned if necessary. Note that, the outlet 700 may be formed in the first glass substrate 200.

The third step is a step (sealing material formation step) of forming the frame 410 and the partition 420. In the third step, the material (the first thermal adhesive) of the frame 410 and the material (the second thermal adhesive) of the partition 420 are applied on to the second glass substrate 300 (the first face of the glass plate 310) with a dispenser or the like. Thereafter, the material of the frame 410 and the material of the partition 420 are dried and calcined. For example, the second glass substrate 300 where the material of the frame 410 and the material of the partition 420 are applied is heated at 480° C. for 20 minutes. Note that, the first glass substrate 200 may be heated together with the second glass substrate 300. In other words, the first glass substrate 200 may be heated under the same condition (at 480° C. for 20 minutes) as the second glass substrate 300. By doing so, it is possible to reduce a difference in degree of warp between the first glass substrate 200 and the second glass substrate 300.

The fourth step is a step (spacer placement step) of placing the spacers 70. The fourth step may include placing the multiple spacers 70 in individual predetermined locations on the second glass substrate 300 with a chip mounter. Note that, the multiple spacers 70 are formed in advance. Alternatively, the multiple spacers 70 may be formed by use of known thin film formation techniques. For example, the spacers 70 can be formed by applying resin composition onto the second glass substrate 300.

The fifth step is a step (gas adsorbent formation step) of forming the gas adsorbent 60. In the fifth step, a solution where a power of the getter is dispersed is applied to a predetermined location on the second glass substrate 300 and then dried to thereby form the gas adsorbent 60.

When a process from the first step to the fifth step is completed, the second glass substrate 300 is obtained, on which the frame 410, the partition 420, the gas passage 600, the outlet 700, the gas adsorbent 60, and the multiple spacers 70 are formed as shown in FIG. 4.

The sixth step is a step (placing step) of placing the first glass substrate 200 and the second glass substrate 300. In the sixth step, the first glass substrate 200 and the second glass substrate 300 are placed so that the second face of the glass plate 210 and the first face of the glass plate 310 face and are parallel to each other. FIG. 5 shows a step of placing the first glass substrate 200 on the second glass substrate 300. Note that, in the present example, members (for example, the frame 410 and the partition 420) are placed on the second glass substrate 300. Alternatively, such members may be placed on the first glass substrate 200.

The assembling step is a step of preparing the temporary assembly 100. In more detail, in the assembling step, the temporary assembly 100 is prepared by bonding the first glass substrate 200 and the second glass substrate 300 to each other. In other words, the assembling step may be referred to as a step (first melting step) of hermetically bonding the first glass substrate 200 and the second glass substrate 300 to each other with the frame 41.

In the first melting step, the first thermal adhesive is melted once at the predetermined temperature (the first melting temperature) equal to or higher than the first softening point and thereby the first glass substrate 200 and the second glass substrate 300 are hermetically bonded to each other. The first glass substrate 200 and the second glass substrate 300 are hermetically bonded to each other with the frame 410. In more detail, the first glass substrate 200 and the second glass substrate 300 are placed in a furnace and heated at the first melting temperature only for predetermined time (the first melting time).

The first melting temperature and the first melting time are selected so that the first glass substrate 200 and the second glass substrate 300 are hermetically bonded to each other with the thermal adhesive of the frame 410 but the gas passage 600 is not closed by the partition 420. In other words, a lower limit of the first melting temperature is equal to the first softening point, and an upper limit of the first melting temperature is however selected so as not to cause the partition 420 to close the gas passage 600. For example, when the first softening point and the second softening point are 434° C., the first melting temperature is set to 440° C. Further, the first melting time may be 10 minutes, for example. Note that, in the first melting step, the frame 410 may emit gas. However such gas may be adsorbed by the gas adsorbent 60.

Through the aforementioned assembling step (the first melting step), the temporary assembly 100 shown in FIG. 6 can be produced. The temporary assembly 100 includes the first glass substrate 200, the second glass substrate 300, the frame 410, the inside space 500, the partition 420, the gas passage 600, the outlet 700, the gas adsorbent 60, and the multiple spacers 70.

The hermetically enclosing step is a step of subjecting the temporary assembly 100 to the above predetermined process to obtain the completed assembly 110. The hermetically enclosing step includes the evacuating step and a melting step (the second melting step). In other words, the evacuating step and the second melting step constitute the above predetermined process.

The evacuating step is a step of converting the evacuation space 510 into the evacuated space 50 by evacuating it by way of the gas passage 600, the gas passage space 520, and the outlet 700 at the predetermined temperature (the evacuating temperature). Like this, heating may be preferably conducted in the evacuating step. This may lead to an increase in the degree of vacuum.

Evacuation can be done by a vacuum pump, for example. As shown in FIG. 6, the vacuum pump is connected to the temporary assembly 100 with the evacuation pipe 810 and a sealing head 820. The evacuation pipe 810 is bonded to the second glass substrate 300 so that an inside of the evacuation pipe 810 is connected to the outlet 700, for example. The sealing head 820 is attached to the evacuation pipe 810, and thereby an inlet of the vacuum pump is connected to the outlet 700.

The first melting step, the evacuating step, and the second melting step are performed with the first glass substrate 200 and the second glass substrate 300 being left in the furnace.

In this regard, the frame 410, the partition 420, the gas passage 600, the outlet 700, the gas adsorbent 60, and the multiple spacers 70 are already provided to the second glass substrate 300. Therefore, an evacuation pipe 810 is bonded to the second glass substrate 300 before the first melting step at the latest.

In the evacuating step, the evacuation space 510 is evacuated by way of the gas passage 600, the gas passage space 520, and the outlet 700 at a predetermined evacuating temperature only for predetermined time (evacuation time). The evacuating temperature is set to be higher than the activation temperature (for example, 350° C.) of the getter of the gas adsorbent 60, and also is set to be lower than the first softening point and the second softening point (for example, 434° C.). The evacuating temperature may be preferably equal to or higher than 300° C. For example, the evacuating temperature is 390° C. According to the above settings, deformation of the frame 410 and the partition 420 is unlikely to occur. Further, the getter of the gas adsorbent 60 is activated, and thus molecules (gas) adsorbed on the getter are desorbed from the getter. Such molecules (that is, gas) desorbed from the getter are discarded through the evacuation space 510, the gas passage 600, the gas passage space 520, and the outlet 700. Therefore, in the evacuating step, the adsorbability of the gas adsorbent 60 is recovered. The evacuation time is set to obtain the evacuated space 50 having a desired degree of vacuum (for example, a degree of vacuum equal to or lower than 0.1 Pa). For example, the evacuation time is set to 120 minutes.

The second melting step is a step of forming the seal 40 enclosing the evacuated space 50 by changing the shape of the partition 420 to form the separator 42 closing the gas passage 600. In the second melting step, the second thermal adhesive is melted once at the predetermined temperature (the second melting temperature) equal to or higher than the second softening point, and thereby the partition 420 is changed in shape to form the separator 42. In more detail, the first glass substrate 200 and the second glass substrate 300 are heated at the second melting temperature for the predetermined time (the second melting time) in the furnace.

The second melting temperature and the second melting time are set to allow the second thermal adhesive to soften to form the separator 42 closing the gas passage 600. A lower limit of the second melting temperature is equal to the second softening point (434° C.). Note that, differently from the first melting step, the purpose of the second melting step is to change the shape of the partition 420, and consequently the second melting temperature is set to be higher than the first melting temperature (440° C.). For example, the second melting temperature is set to 460° C. Additionally, the second melting time is, for example, 30 minutes.

When the separator 42 is formed, the evacuated space 50 is separated from the gas passage space 520. Hence, the vacuum pump cannot evacuate the evacuated space 50. The frame 410 and the separator 42 are heated until the second melting step is finished, and therefore gas may be emitted from the frame 410 and the separator 42. However, gas emitted from the frame 410 and the separator 42 is adsorbed on the gas adsorbent 60 inside the evacuated space 50. Consequently, a decrease in the degree of vacuum of the evacuated space 50 can be suppressed. In summary, it is possible to suppress a decrease in the thermal insulating properties of the glass panel unit 10.

Also in the first melting step, the frame 410 and the separator 42 are heated. Thus, the frame 410 and the separator 42 may emit gas. Gas emitted by the frame 410 and the separator 42 is adsorbed by the gas adsorbent 60, and therefore the adsorbability of the gas adsorbent 60 may decrease due to the first melting step. However, in the evacuating step, the evacuation space 510 is evacuated at the evacuating temperature equal to or higher than the activation temperature of the getter of the gas adsorbent 60 and thereby the adsorbability of the gas adsorbent 60 is recovered. Therefore, the gas adsorbent 60 can adsorb a sufficient amount of gas emitted from the frame 410 and the separator 42 in the second melting step. In other words, it is possible to avoid an undesired situation the gas adsorbent 60 fails to adsorb a sufficient amount of gas emitted from the frame 410 and the separator 42 and thus the degree of vacuum of the evacuated space 50 decreases.

Additionally, in the second melting step, evacuation of the evacuation space 510 through the gas passage 600, the gas passage space 520, and the outlet 700 is continued from the evacuating step. In other words, in the second melting step, the separator 42 closing the gas passage 600 is formed by changing the shape of the partition 420 at the second melting temperature while the evacuation space 510 is evacuated through the gas passage 600, the gas passage space 520, and the outlet 700. By doing so, it is possible to further lower a probability that the degree of vacuum of the evacuated space 50 decreases during the second melting step. Note that, the second melting step does not necessarily include evacuating the evacuation space 510 through the gas passage 600, the gas passage space 520, and the outlet 700.

The above predetermined process includes converting the evacuation space 510 into the evacuated space 50 by evacuating the evacuation space 510 by way of the gas passage 600, the gas passage space 520, and the outlet 700 at a predetermined temperature (evacuating temperature). The evacuating temperature is higher than the activation temperature of the getter of the gas adsorbent 60. Consequently, evacuation of the evacuation space 510 and recovery of the adsorbability of the getter can be performed simultaneously.

The above predetermined process further includes forming the seal 40 enclosing the evacuated space 50 by forming a separator 42 for closing the gas passage 600 by changing a shape of the partition 420 (see FIG. 8). The partition 420 includes the second thermal adhesive. Therefore, the separator 42 can be formed by changing the shape of the partition 420 by once melting the second thermal adhesive at a predetermined temperature (second melting temperature) equal to or higher than the second softening point. Note that, the first melting temperature is lower than the second melting temperature. Consequently, it is possible to prevent the gas passage 600 from being closed due to deformation of the partition 420 in bonding the first glass substrate 200 and the second glass substrate 300 with the frame 410. Note that, the partition 420 may be made of material which is more deformable than that of the frame 410 when melted.

The partition 420 is changed in shape so that the first closing part 4221 closes the first gas passage 610 and the second closing part 4222 closes the second gas passage 620. The separator 42, which is obtained by changing the shape of the partition 420 as described above, separates (spatially) the evacuated space 50 from the gas passage space 520. The separator (second part) 42 and part (first part) 41 of the frame 410 corresponding to the evacuated space 50 constitute the seal 40 enclosing the evacuated space 50.

The evacuated space 50 is obtained by evacuating the evacuation space 510 by way of the gas passage space 520 and the outlet 700 as described above. The evacuated space 50 is hermetically enclosed by the first glass substrate 200, the second glass substrate 300, and the seal 40 completely and thus is separated from the gas passage space 520 and the outlet 700.

Additionally, the seal 40 with a rectangular frame shape is formed. The seal 40 includes the first part 41 and the second part 42. The first part 41 is part of the frame 410 corresponding to the evacuated space 50. In other words, the first part 41 is part of the frame 410 facing the evacuated space 50. The first part 41 has an almost U-shape, and serves as three of four sides of the seal 40. The second part 42 is a separator formed by changing the shape of the partition 420. The second part 42 has an I-shape, and serves as a remaining one of the four sides of the seal 40.

In the evacuating step, forces may arise to move the first glass substrate 200 and the second glass substrate 300 close to each other. However, the spacers 70 keep the space between the first glass substrate 200 and the second glass substrate 300.

In this regard, when the height of the spacer 70 is set to be smaller than the height of the seal 40, the first glass panel 20 and the second glass panel 30 are bonded to each other with the seal 40 being compressed. When bonding is made with compression as described above, the two glass panels can be bonded to each other to have high strength. In particular, strength can be improved at a vicinity of the seal 40.

Through the aforementioned hermetically enclosing step, the completed assembly 110 shown in FIG. 7 to FIG. 9 is produced. The completed assembly 110 includes the first glass substrate 200, the second glass substrate 300, the seal 40, the evacuated space 50, the gas passage space 520, the gas adsorbent 60, and the multiple spacers 70. Note that, in FIG.

8, to facilitate understanding of the internal structure only, the first glass substrate 200 is illustrated with part (right and lower part) thereof being cutaway.

The removing step is a step of obtaining the glass panel unit 10 which is part including the evacuated space 50, by removing part 11 including the gas passage space 520 from the completed assembly 110. As shown in FIG. 8, in more detail, the completed assembly 110 taken out from the furnace is cut along the cutting line 900, and thereby is divided into predetermined part (glass panel unit) 10 including the evacuated space 50 and part (unnecessary part) 11 including the gas passage space 520. The unnecessary part 11 mainly includes part 230 of the first glass substrate 200 corresponding to the gas passage space 520, part 320 of the second glass substrate 300 corresponding to the gas passage space 520, and part 411 of the frame 410 corresponding to the gas passage space 520. Note that, in consideration of production cost of the glass panel unit 10, the unnecessary part 11 is preferably as small as possible. FIG. 10 shows removing the unnecessary part 11 from the completed assembly 110.

Cutting is done by an appropriate cutting device. Examples of the cutting device may include a scriber and a laser. By cutting the first glass substrate 200 and the second glass substrate 300 at the same time, the glass panel unit 10 can be cut efficiently. Note that, the shape of the cutting line 900 is set according to the shape of the glass panel unit 10. The glass panel unit 10 is rectangular, and therefore the cutting line 900 is a straight line along the lengthwise direction of the wall 42.

Through the aforementioned preparation step, assembling step, hermetically enclosing step, and removing step, the glass panel unit 10 as shown in FIG. 1 and FIG. 2 is produced. The first glass panel 20 is part of the first glass substrate 200 corresponding to the evacuated space 50. The second glass panel 30 is part of the second glass substrate 300 corresponding to the evacuated space 50. The outlet 700 for forming the evacuated space 50 is present in the part 320 of the second glass substrate 300 corresponding to the gas passage space 520, and the evacuation pipe 810 is connected to the part 320. Therefore, the outlet 700 is not present in the second glass panel 30.

Hereinafter, optional modifications relating to the glass panel unit are described. In the description relating to the modifications, the reference sings in parentheses of corresponding components are introduced.

In the above embodiment, the glass panel unit (10) is rectangular, but the glass panel unit (10) may have a desired shape such as a circular shape and a polygonal shape. Stated differently, each of the first glass panel (20), the second glass panel (30), and the seal (40) does not need to be rectangular and may have a desired shape such as a circular shape and a polygonal shape. Note that, the shapes of the first glass substrate (200), the second glass substrate (300), the frame (410), and, the separator (42) are not limited to the shapes described in the explanation of the above embodiment, and may have such shapes that the glass panel unit (10) can have a desired shape. Note that, the shape and size of the glass panel unit (10) may be determined in consideration of application of the glass panel unit (10).

Additionally, the first face and the second face, of the body (21) of the first glass panel (20) are not limited to flat faces. Similarly, the first face and the second face, of the body (31) of the second glass panel (30) are not limited to flat faces.

Additionally, the body (21) of the first glass panel (20) and the body (31) of the second glass panel (30) do not need to have the same plan shape and plan size. Further, the body (21) and the body (31) do not need to have the same thickness. Furthermore, the body (21) and the body (31) do not need to be made of the same material. Similarly, the glass plate (210) of the first glass substrate (200) and the glass plate (310) of the second glass substrate (300) do not need to have the same plan shape and plan size. Further, the glass plate (210) and the glass plate (310) do not need to have the same thickness. Furthermore, the glass plate (210) and the glass plate (310) do not need to be made of the same material.

Additionally, the seal (40) do not need to have the same plan shape with the first glass panel (20) and the second glass panel (30). Similarly, the frame (410) do not need to have the same plan shape with the first glass substrate (200) and the second glass substrate (300).

Additionally, the first glass panel (20) may include a coating which has desired physical properties and is formed on the second flat face of the body (21). Alternatively, the first glass panel (20) does not need to include the coating (22). In other words, the first glass panel (20) may be constituted by the body (21) only.

Additionally, the second glass panel (30) may include a coating with desired physical properties. For example, the coating may include at least one of thin films formed on the first flat face and the second flat face of the body (31) respectively. Examples of the coating may include a film reflective for light with a specified wavelength (for example, infrared reflective film and ultraviolet reflective film).

In the above embodiment, the frame (410) is made of the first thermal adhesive. However, the frame (410) may include other component such as a core, in addition to the first thermal adhesive. Stated differently, it is sufficient that the frame (410) includes the first thermal adhesive. In the above embodiment, the frame (410) is formed to surround an almost entire region on the second glass substrate (300). However, it is sufficient that the frame (410) is formed to surround a predetermined region on the second glass substrate (300). In other words, there is no need to form the frame (410) so as to surround an almost entire region on the second glass substrate (300). Alternatively, the completed assembly (110) may include two or more frames (410). In other words, the completed assembly (110) may include two or more inside spaces (500). In this case, it is possible to produce two or more glass panel units (10) from one completed assembly (110).

In the above embodiment, the partition (420) is made of the second thermal adhesive. However, the partition (420) may include other component such as a core, in addition to the second thermal adhesive. Stated differently, it is sufficient that the partition (420) includes the second thermal adhesive. Further, in the above embodiment, the partition (420) has its opposite end not connected to the frame (410). And, gaps between the opposite ends of the partition (420) and the frame (410) define the gas passages (610, 620). However, the partition (420) may have only one of its opposite ends not connected to the frame (410). In this case, there is one gas passage (600) between the partition (420) and the frame (410). Alternatively, the partition (420) may have its opposite end both connected to the frame (410). In this case, the gas passage (600) may be a through hole formed in the partition (420). Alternatively, the gas passage (600) may be a gap between the partition (420) and the first glass substrate (200). Alternatively, the partition (420) may be defined as a set of two or more partitions spaced from each other. In this case, the gas passage (600) may be a gap between adjacent two of the two or more partitions.

In the above embodiment, the inside space (500) is divided into one evacuation space (510) and one gas passage space (520). Note that, the inside space (500) may be divided into one or more evacuation spaces (510) and one or more gas passage spaces (520). When the inside space (500) includes two or more evacuation spaces (510), it is possible to produce two or more glass panel units (10) from one completed assembly (110).

In the above embodiment, the second thermal adhesive is identical to the first thermal adhesive, and the second softening point is equal to the first softening point. However, the second thermal adhesive may be different material from the first thermal adhesive. For example, the second thermal adhesive may have the second softening point different from the first softening point of the first thermal adhesive. In such a case, the second softening point may be preferably higher than the first softening point. In this case, the first melting temperature can be set to be equal to or higher than the first softening point and lower than the second softening point. By doing so, it is possible to suppress undesired deformation of the partition 420 in the first melting step.

Additionally, each of the first thermal adhesive and the second thermal adhesive are not limited to glass frit, and may be selected from low-melting-point metal, hot-melt adhesive, and the like, for example.

In the above embodiment, a furnace is used to heat the frame (410), the gas adsorbent (60), and the partition (420). However, such heating can be done with appropriate heating means. Examples of the heating means may include a laser and a thermally conductive plate connected to a heat source.

In the above embodiment, the gas passage (600) includes the two gas passages (610, 620). However, the gas passage (600) may include only one gas passage or may include three or more gas passages. Further, the shape of the gas passage (600) are not limited in particular.

In the above embodiment, the outlet (700) is formed in the second glass substrate (300). However, the outlet (700) may be formed in the glass plate (210) of the first glass substrate (200) or may be formed in the frame (410). In summary, the outlet (700) may be allowed to be formed in the unnecessary part (11).

In the above embodiment, the getter of the gas adsorbent (60) is an evaporative getter. However, the getter may be a non-evaporative getter. When the non-evaporative getter has a temperature equal to or higher than a predetermined temperature (the activation temperature), adsorbed molecules intrudes into an inside of the getter, and thus the adsorbability can be recovered. In contrast to the evaporative getter, the adsorbed molecules are not desorbed. Therefore, after the non-evaporative getter has adsorbed an amount of molecules equal to or more than a certain amount, the adsorbability is no longer recovered even if the getter is heated up to a temperature equal to or higher than the activation temperature.

In the above embodiment, the gas adsorbent (60) has an elongated shape, but may have another shape. Additionally, the gas adsorbent (60) does not necessarily need to be positioned at the end of the evacuated space (50). Further, in the above embodiment, the gas adsorbent (60) may be formed by applying a liquid containing a powder of the getter (for example, a dispersion liquid prepared by dispersing a powder of the getter in a liquid, and a solution prepared by dissolving a powder of the getter in a liquid). However, the gas adsorbent (60) may include a substrate and the getter fixed to the substrate. This type of the gas adsorbent (60) may be formed by immersing a substrate in a liquid containing the getter and drying it. Note that, the substrate may have a desired shape, but may be an elongated rectangular shape, for example.

Alternatively, the gas adsorbent (60) may be a film formed entirely or partially on the surface (first face) of the glass plate (310) of the second glass substrate (300). This type of the gas adsorbent (60) may be formed by coating the surface (first face) of the glass plate (310) of the second glass substrate (300) with a liquid containing a powder of the getter.

Alternatively, the gas adsorbent (60) may be included in the spacer (70). For example, the spacer (70) may be made of material containing the getter, and thereby the spacer (70) including the gas adsorbent (60) can be obtained. When the spacer (70) is a stack of polymer films, bond for bonding the polymer films to each other may include the getter, for example.

Alternatively, the gas adsorbent (60) may be solid material made of the getter. This gas adsorbent (60) tends to have a large size, and thus cannot be placed between the first glass substrate (200) and the second glass substrate (300) in some cases. In such cases, the glass plate (310) of the second glass substrate (300) may be formed to include a recess, and the gas adsorbent (60) may be placed in this recess.

Alternatively, the gas adsorbent (60) may be preliminarily placed in a package to suppress the getter from adsorbing molecules. In this case, the package may be broken after the second melting step to expose the gas adsorbent (60) to the evacuated space (50).

In the above embodiment, the glass panel unit (10) includes the gas adsorbent (60). However, the glass panel unit (10) does not need to include any gas adsorbent (60).

In the above embodiment, the glass panel unit (10) includes the multiple spacers (70). However, the glass panel unit (10) may include a single spacer (70).

The present embodiment relates to forming the glass panel unit (10) not including an outlet by removing the unnecessary part (11). In one case, the glass panel unit (10) may include an outlet. In this case, at least one of the first glass panel (20) and the second glass panel (30) may include an outlet. The outlet is closed to keep the evacuated space (50) in the vacuum state. When at least one of the first glass panel (20) and the second glass panel (30) includes such an outlet, the outlet may be closed with a cap. However, to improve an appearance, it is preferable that the glass panel unit (10) do not include the outlet.

FIG. 11 shows a modification of the glass panel unit (referred to as a glass panel unit 10A). In the glass panel unit 10A, the second glass panel 30 includes an outlet 700. The outlet 700 is closed by a seal 81. Accordingly, the evacuated space 50 can be kept in a vacuum state. The seal 81 is made of the evacuation pipe 810. The seal 81 can be made by melting glass forming the evacuation pipe 810. There is a cap 80 disposed outside the seal 81. The cap 80 covers the seal 81. By covering the seal 81 with the cap 80, the outlet 700 can be closed securely. Additionally the cap 80 can suppress breakage of surrounding part of the outlet 700. The glass panel unit 10A is same as the glass panel unit 10 shown in FIG. 1 and FIG. 2 except for the outlet 700, the seal 81, and the cap 80 being provided. The same components as the glass panel unit 10 shown in FIG. 1 and FIG. 2 are designated by the same reference signs as the glass panel unit 10 shown in FIG. 1 and FIG. 2, and descriptions with reference to FIG. 1 and FIG. 2 can apply to the same components. The glass panel unit 10A can be produced by a method in accordance with the production method of the temporary assembly 100. The glass panel unit 10A does not require removal of part including the outlet 700, and thus production therefore can be facilitated.

FIG. 12 shows a modification of the glass panel unit (referred to as a glass panel unit 10B). In the glass panel unit 10B, the outlines of the first glass panel 20 and the second glass panel 30 are not aligned with each other in a plan view. One of the glass panels (that is, the first glass panel 20) is smaller than the other (that is, the second glass panel 30). In the glass panel unit 10B, the seal 40 protrudes outside from the space between the first glass panel 20 and the second glass panel 30. In this case, the height H2 of the seal 40 is defined as a height of part, between the first glass panel 20 and the second glass panel 30, of the seal 40. The glass panel unit 10B is same as the glass panel unit 10A shown in FIG. 11 but is different from it in a structure of end parts. The same components as the glass panel unit 10 shown in FIG. 1 and FIG. 2 as well as the glass panel unit 10A shown in FIG. 11 are designated by the same reference signs as the glass panel unit 10 shown in FIG. 1 and FIG. 2 as well as the glass panel unit 10A shown in FIG. 11, and descriptions with reference to FIG. 1 and FIG. 2 as well as FIG. 11 can apply to the same components.

EXAMPLE

As for glass panel units, differences between physical properties resulting from differences between the heights of the spacers were examined. The spacers were made of a stack of films of polyimide with benzoxazole structures. The height of the spacer was adjusted by changing the thicknesses of the films of polyimide and the number of the films in the stack. The films of polyimide were formed of “XENOMAX” (registered trademark) available from TOYOBO CO.,LTD. The height of the seal was adjusted by changing the size of the particle. The particle used has a particle size of 132 μm. Thus, the height of the seal is 132 μm. The spacer has a diameter of 500 μm.

FIG. 13 is a graph illustrating results of test by a free falling ball method for glass panel units. The test by the free falling ball method can give an index of resistance to impact which is defined as an average height (falling-ball height, unit: cm) from which a ball with a weight of 225 g falls into a glass panel unit and a surface of the glass panel unit is damaged. The heights of the spacer and the seal mean the heights of the spacers and the seal after formation of the glass panel unit, respectively.

As shown in FIG. 13, it can be understood that, when the height of the spacer is smaller than the height of the seal, the falling-ball height can be increased and the resistance to impact can be improved. 

1. A glass panel unit comprising: a first glass panel; a second glass panel placed opposite the first glass panel; a seal with a frame shape hermetically bonding the first glass panel and the second glass panel to each other; an evacuated space enclosed by the first glass panel, the second glass panel, and the seal; and at least one spacer placed between the first glass panel and the second glass panel, the at least one spacer having a height smaller than a height of the seal between the first glass panel and the second glass panel.
 2. The glass panel unit of claim 1, wherein outlines of the first glass panel and the second glass panel are aligned with each other in a plan view.
 3. The glass panel unit of claim 1, wherein the seal includes material for keeping a distance between the first glass panel and the second glass panel.
 4. The glass panel unit of claim 2, wherein the seal includes material for keeping a distance between the first glass panel and the second glass panel. 